The crawler robot, which started its work Wednesday, is the same model as the one Tepco dispatched last Friday. The initial machine became immovable after recording some footage from inside the reactor and covering about two-thirds of the originally planned route. The utility cut the cables connected to the machine after giving up on retrieving it. It was the first time a robot ventured inside one of the containment vessels following the 2011 nuclear crisis.

According to Tepco, the second machine will go inside the containment vessel from a different route. Because the robots appear better able to withstand radiation than initially expected, the company will take more time to move the machine and choose its path. If all goes well, the second robot might be operational inside the vessel for two to three days, the utility said.